Oscillating Device For Generating Seismic Loads And Compacting Soil

ABSTRACT

A mobile oscillator device that employs two counter-rotating masses that generate a large impact force at multiple frequencies without generating forces in other undesired directions.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 61/330,239 filed Apr. 30, 2010, entitled OSCILLATING DEVICE FOR GENERATING SEISMIC LOADS AND COMPACTING SOIL, the contents of which are incorporated in their entirety herein.

FIELD OF THE INVENTION

The present invention relates to devices and associated methods for producing seismic forces and, more particularly, to producing large repetitive forces using relatively lightweight vehicles.

BACKGROUND OF THE INVENTION

It is often desirable to employ a relatively lightweight vehicle to generate a large, repetitive, seismic force for duties such as soil compaction and/or demining purposes. The seismic force must be generated while minimizing interference with the vehicle's handling, stability, and structural integrity. Furthermore, it is desirable that the mechanism that generates the seismic load be robust enough to withstand not only the relatively large repetitive force but, in the case of demining vehicles, also withstand blast events. It order to more efficiently utilize resources, it is also desirable that the mechanism used to generate the seismic force be a stand-alone accessory that is relatively easily transferrable between different vehicles.

OBJECTS AND SUMMARY OF THE INVENTION

The present invention provides an oscillator device employing two counter-rotating masses that generate a large impact force at multiple frequencies. In one embodiment of the device of the present invention the device has an oscillating mode and an impact mode. In another embodiment of the present invention the device has only an impact mode.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which:

FIG. 1 is a perspective view of one embodiment of an oscillating device according to the present invention.

FIG. 2 is a free body diagram of one embodiment of an oscillating device according to the present invention.

FIG. 3 is a cross-sectional view of one embodiment of an oscillating device according to the present invention.

FIG. 4 is a perspective view of one embodiment of an oscillating device according to the present invention.

FIG. 5 is a cross-sectional view of one embodiment of an oscillating device according to the present invention.

FIG. 6 is a perspective view of one embodiment of an oscillating device according to the present invention.

FIG. 7 is a perspective view of a portion of one embodiment an oscillating device according to the present invention.

FIG. 8 is a side elevation view of a portion of one embodiment of an oscillating device according to the present invention.

FIG. 9 is a perspective of a portion of one embodiment of an oscillating device according to the present invention.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

The oscillator device of the present invention is operable to generate large ground impact forces at multiple operating frequencies without generating forces in other undesired orientations that could adversely affect dynamic stability and/or cause structural, fatigue-inducing vibration in the vehicle to which the device is attached. The oscillator device of the present invention is configured around two synchronized, counter-rotating masses that produce a force that is purely normal to the suspension arm when the arm is coupled to a drive motor. One advantage of the present invention is that the motion created by the oscillator is purely harmonic, thereby minimizing the amount of energy input to create the desired seismic signals.

In one embodiment of the present invention, shown in FIGS. 1-3, a device 5 has two operational modes, an oscillating mode and a tractive mode. With reference to FIG. 2A, in the oscillating mode the device 5 generates a repetitive seismic force in the direction of arrow 5, and in the tractive mode the device 5 generates tractive effort in the direction of arrow 7 that assists in propelling the vehicle to which it is attached. Broadly speaking, the device 5 employs a wheel 22 that is attached to a vehicle by a vehicle road arm 10. A rotating shaft power is transmitted from a power source, for example a power source mounted or incorporated into the vehicle chassis, through the road arm pivot shaft 11. Attached to road arm pivot shaft 11 is an upper pulley 12. A chain or belt 13 is associated with the upper pulley 12 and a lower pulley 14 and serves to transfer the rotating shaft power from the upper pulley 12 to the lower pulley 14. The lower pulley 14 is attached to a lay shaft 15.

When operating in oscillating mode, the lay shaft 15 drives a counter-rotation gearset 16. The counter-rotation gearset 16 simultaneously rotates an inner spindle 17 and an outer spindle 19 in opposite directions as indicated by arrows 9, shown in FIG. 2A. As shown in FIG. 3, the inner spindle 17 is positioned through the outer spindle 19, both of which are positioned substantially through an axis of rotation 8 of the wheel 22. The inner spindle 17 is attached to an inner oscillator mass 18 and the outer spindle 19 is attached to an outer oscillator mass 20. The inner oscillator mass 18 and the outer oscillator mass 20 are each attached to their respective spindles by yokes 21 which secure the masses at appropriate distances from the axis of rotation 8.

Since the inner spindle 17 and the outer spindle 19 to which the oscillator mass 18 and the oscillator mass 20 are attached, respectively, are rotating in opposite directions, the oscillator masses 18 and 20 are also counter-rotated about the axis 8. In order to accommodated for the counter-rotation of the oscillator masses 18 and 20 within the confined space of the wheel 22, the oscillator masses 18 and 20 have rotate at different orbits about the axis 8. That is to say, the yokes attaching the oscillator masses 18 and 20 the spindles 17 and 19, respectively, secure the oscillator mass 18 at a different length from the axis 8 than the oscillator mass 20 is secured from the axis 8. For example, as shown in FIG. 3, the oscillator mass 18 rotates about the axis 8 at an orbit closer to the axis 8 than the orbit of the oscillator mass 20, i.e. the oscillator mass 18 rotates within the orbit of the oscillator mass 20.

Consequently, in order to maintain symmetry within the system, the masses of the oscillator masses 18 and 20 are unequal. The outer oscillator mass 20 is smaller than inner oscillator mass 18; however, in view of their different orbits about the axis 8, the oscillator masses 18 and 20 are proportionate to each other so that they both generate equal centripetal forces when rotated at the same angular velocity. The counter-rotation gearset 16 synchronizes the motion of both of the oscillator masses 18 and 20 such that they both rotate at the same angular velocity, one clockwise and the other counter-clockwise, and such that the oscillator masses 18 and 20 both reach their maximum vertical position simultaneously and their minimum vertical position simultaneously. When synchronized in this manner, the horizontal forces generated by each oscillator mass 18, 20 are equal and opposite the other oscillator mass 18, 20. Accordingly, the horizontal forces of the oscillator masses 18 and 20 cancel each other out and the device 5 effectively transmitting no horizontal forces to the vehicle to which it is attached. The vertical forces generated by the oscillator masses 18 and 20 are equal and additive, thereby producing a purely vertical resultant force.

When tractive effort is desired instead of oscillating forces, a dog clutch 23 is employed to disengage the lay shaft 15 from the counter-rotation gearset 16 and to engage the lay shaft 15 with a drive gearset 24. The driven gear of drive gearset 24 is mounted to drive shaft 25. Drive shaft 25 is affixed to outer wheel hub 26 which is in turn affixed to road wheel 22. As shown in FIG. 3, the outer wheel hub 26 and the drive shaft 25 together form a housing around, in part, the counter rotating masses 18, 20. While operating in tractive mode, the rotating shaft power transmitted from the power source to the road arm pivot shaft 11 is employed to apply torque to the road wheel instead of to the oscillating weight set, causing the wheel to function similar to the driven wheels of an automobile.

In a second embodiment of the present invention, shown in FIGS. 4 and 5, a device 105 has only a single, oscillating operational mode. Broadly speaking, the device 105 employs a wheel 122 that is mounted to vehicle by a vehicle road arm 110. A power source, for example hydraulic power, is delivered from the vehicle chassis to the hydraulic motor 111. It is contemplated that a variety of alternate power transmission techniques can also be used, such as the shaft power described above for use in the dual-mode device 5 or electrical power delivered to an electrical motor mounted in place of the hydraulic motor 111. A drive sprocket 112 transmits power from the hydraulic motor 111 to a driven sprocket 114 through a drive belt or chain 113. The driven sprocket 114 is mounted to an input shaft 115 of a counter-rotation gearset 116.

The counter-rotation gearset 116 is similar to the counter-rotating gearset 16 described above for the device 5. The counter-rotating gearset 116 synchronizes the rotation of the inner oscillator mass 118 and the outer oscillator mass 119 about an axis 108 of the wheel 122 such that the inner oscillator mass 118 and the outer oscillator mass 119 both rotate at the same angular velocity, one clockwise and the other counter-clockwise and that both oscillator masses 118 and 120 reach their maximum vertical position simultaneously and both reach their minimum vertical position simultaneously.

Torque is transmitted to the inner oscillator mass 118 by an inner drive shaft 117 to which to inner oscillator mass 118 is affixed. Torque is transmitted to the outer oscillator mass 119 by an outer drive shaft 120. One or both of the oscillator masses 118 and 120 may be attached to their respective drive shafts 117 and 119 by yokes 121. The yokes 121 secure the oscillator mass 118, 120 to the drive shafts 117, 119 at appropriate distances from the axis of rotation 8.

Both the inner drive shaft 118 and the outer drive shaft 119 are concentrically aligned with the axis 108 and nested within at least one wheel spindle 124. At least one wheel bearing 126 is affixed to the road arm 110 and supports a wheel spindle 124, allowing it to freely spin about the axis of rotation 108. The wheel spindle 124 is affixed to at least one side plate 123, which is turn attached to the road wheel 122. The road wheel 124 transmits impact forces generated by the inner oscillator mass 116 and the outer oscillator mass 117 into the terrain being traversed by the vehicle.

In a third embodiment of the present invention, shown in FIGS. 6-9, a device 205 has an alternatively configured oscillating operational mode. The device employs a road wheel 222 that is mounted to a vehicle by a vehicle road arm 210. A wheel spindle 240 is affixed to road arm 210 and supports at least one wheel bearing 226. An outer race of the wheel bearing 226 is affixed to at least one side of a plate 242. The plate 242 is mounted to the road wheel 222 allowing the road wheel 222 to freely turn about the wheel spindle 240 and transmit impact forces generated by the oscillating device to the terrain being traversed by the vehicle.

An oscillator housing 244 is affixed to at least one of the wheel spindles 240 such that the oscillator housing 244 does not rotate about an axis of rotation 208. The oscillator housing 244 includes a compartment 245 accessed by front cover plate 246. The compartment 245 contains a first oscillator gear 248 and a second oscillator gear 250. The first oscillator gear 248 is affixed to a drive shaft 249, and the second oscillator gear 250 is affixed to an auxiliary shaft 251. The first oscillator gear 248 and the second oscillator gear 250 mesh with one another such that when the first oscillator gear 248 rotates in the clockwise direction, the second oscillator gear 250 rotates in the counterclockwise direction.

As shown in FIG. 9, the drive shaft 249 is driven by a motor 256 that is attached to a back side 258 of the oscillator housing 244. The motor 256 may, for example, be an electric motor. The motor 256 is attached to the drive shaft 249 and is positioned outside of the compartment 245 of the oscillator housing 244. Placement of the motor 256 outside of the compartment 245 is advantageous in that the gears and other components housed within the compartment 245 may be lubricated or serviced without contaminating or otherwise compromising the performance of the motor 256.

The first oscillator gear 248 and the identical second oscillator gear 250 each include at least one eccentric lightening hole 252. The eccentric lightening hole 252 serves to offset the center of mass of each gear from its pitch center, thereby causing the first oscillator gear 248 and the second oscillator gear 250 to act as synchronized, counter-rotating oscillator masses similar to those described above regarding the devices 5 and 105. The offset center of mass can be further increased by varying the size, number and location of lightening holes 252 and by employing one or more counterweights, not shown, opposite the holes 252. The counterweights may, for example, be attached to the first oscillator gear 248 and the second oscillator gear 250 gear by using counterweight mount holes 254. For the sake of clarity, it is noted that the rotation of road wheel 222 is independent of the oscillator motion.

The oscillator device of the present invention has a number of features which increase its resistance to damage, such as damage caused by a blast event resulting from detonation of a landmine. For example, in embodiments employing a drive chain or belt, the system is configured to accommodate large amounts of transient arm bending and torsional deflection produced during a blast event without becoming misaligned. Furthermore, the oscillator components are fully enclosed in the integral wheel hub and spindle or within the oscillator housing, thereby protecting them from foreign object damage and fully containing them within the wheel rim. A monolithic wheel not only keeps damaged oscillator components from causing damage to other vehicle components or bystanders in the work zone, it also acts as a natural shield to protect the rotating components from impact damage during a blast event and foreign object damage during operation in rough terrain.

Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof. 

1. A device for producing a repetitive force comprising: an input shaft; a wheel connected to the input shaft; and two counter-rotating masses attached to the wheel.
 2. The device of claim 1 wherein the input shaft is driven by a motor.
 3. The device of claim 1 wherein the input shaft is connected to the wheel by a chain or belt.
 4. The device of claim 3 wherein the chain or belt rotates a layshaft that is connected to a clutch.
 5. The device of claim 4 wherein the clutch is configured to engage a traction gearset attached to the wheel.
 6. The device of claim 1 wherein the two counter-rotating masses rotate about an axis of the wheel.
 7. The device of claim 1 wherein the two counter-rotating masses are asymmetric.
 8. The device of claim 1 wherein the two counter-rotating masses are coplanar.
 9. The device of claim 1 wherein a force that is normal to a suspension arm of the device is produced during rotation of the two counter rotating masses.
 10. The device of claim 1 wherein the device further comprises ballast.
 11. A method for generating seismic loads comprising: providing a wheel having a suspension arm connected to a vehicle; and generating a force normal to the suspension arm.
 12. The method of claim 11 wherein the step of generating a force normal to the suspension arm comprises rotating two counter-rotating masses about an axis of the wheel.
 13. The method of claim 12 wherein the step of rotating two counter-rotating masses about an axis of the wheel comprises rotating two coplanar counter-rotating masses.
 14. The method of claim 12 wherein the step of rotating two counter-rotating masses about an axis of the wheel comprises rotating two asymmetric counter-rotating masses.
 15. The method of claim 12 wherein the step of rotating two counter-rotating masses about an axis of the wheel comprises driving a counter-rotational gearset with a layshaft reversibly connected to the counter-rotational gearset and a traction gearset.
 16. The method of claim 11 wherein the step of generating a force normal to the suspension arm comprises rotating two counter-rotating masses about an axes other than an axis of the wheel.
 17. A device for generating seismic loads comprising: an input shaft driving a layshaft, the lay shaft reversibly engaged to a traction gearset and a counter-rotational gearset; two counter rotating masses attached to the counter-rotational gearset; and a wheel attached to the traction gearset.
 18. The device of claim 17 wherein the two counter-rotating masses are coplanar.
 19. The device of claim 17 wherein the two counter-rotating masses are asymmetric.
 20. The device of claim 17 wherein rotation of the two counter-rotating masses results in a force normal to a suspension arm connecting the wheel to a vehicle.
 21. The device of claim 17 wherein the two counter-rotating masses rotate about an axis of the wheel. 